Staging Environment: Content and features may be unstable or change without notice.
Advisory details: gitlab / pypi/nltk/CVE-2026-63312
Advisory ID gitlab/pypi/nltk/CVE-2026-63312
Aliases CVE-2026-63312
GHSA-x5ph-mj9p-rfr8
Summary NLTK: StreamBackedCorpusView Bypasses pathsec.ENFORCE - Arbitrary Local File Read Setting `nltk.pathsec.ENFORCE = True` is documented to sandbox all file access to allowed NLTK data directories and raise `PermissionError` on unauthorized access. However, `StreamBackedCorpusView` opens files via `builtins.open()` directly, bypassing `pathsec.validate_path()` entirely. An attacker who can influence the `fileid` argument can read arbitrary local files regardless of the `ENFORCE` setting.
Status Published
Exploitability 0.5
Weighted Severity 0.0
Risk
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (3)
CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
cvssv3.1 https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-63312.yml
Reference id Reference type URL
https://github.com/nltk/nltk/commit/674ea75accdf08eca3782dee0a9c4ed7e0d0025b
https://github.com/nltk/nltk/pull/3588
https://github.com/nltk/nltk/releases/tag/v3.10.0
https://github.com/nltk/nltk/security/advisories/GHSA-x5ph-mj9p-rfr8
https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3730.yaml
https://www.vulncheck.com/advisories/nltk-streambackedcorpusview-bypasses-pathsec-enforce-arbitrary-file-read
CVE-2026-63312 https://nvd.nist.gov/vuln/detail/CVE-2026-63312
GHSA-x5ph-mj9p-rfr8 https://github.com/advisories/GHSA-x5ph-mj9p-rfr8
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Found at https://gitlab.com/gitlab-org/advisories-community/-/blob/main/pypi/nltk/CVE-2026-63312.yml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.